The experimental protocol runs on a Palm handheld that is used to provide instructions to the tester, record the subject's responses, and communicate with a PC/monitor at a test distance of 3 meters. Stimuli are high contrast black-and-white ETDRS letters presented on an ultra high resolution FD Trinitron monitor, that subtend 2.5 to 200 min of arc; each letter appears in isolation under equiluminant conditions, and is flanked with black bars to simulate visual crowding.